Magnetic separator



Dec. 27, 1966 D. WESTON MAGNETIC SEPARATOR 5 Sheets-Sheet 1 Filed May31, 1965 Dec. 27, 1966 D. WESTON 3,294,237

MAGNET I C SEPARATOR Filed May 31, 1963 5 Sheets-Sheet 2 L to 9 INVENTORDAV/D [WESTON ATTORNEY.

Dec. 27, 1966 D. WESTON MAGNETIC SEPARATOR 5 Sheets-Sheet I5 Filed May51, 1963 unu nu I U: Ur M rEFB5BII B5 5 d C J J T W F O a w FIG. 3

INVENTOR DAV/D WESTON B Y-XM A TTORNEYS.

Dec. 27, 1966 D. WESTON MAGNETIC SEPARATOR 5 Sheets-Sheet 4 Filed May51, 1963 9 8 4 4 7 4 a 3 M 5 7 I O w 4 6 I... =2: 4 B ig/2i: 2 5- E: E:l: x l 4 J. W H p H m 4 11B M ATTORNEYS.

Dec. 27, 1966 D. WESTON 3,294,237

MAGNETIC SEPARATOR' Filed May 51, 1963 5 Sheets-Sheet '5 FIG. 5

INVENTOR DAVID WESTON ,XM W

ATTORNEYS W'mm United States Patent 3,294,237 MAGNETIC SEPARATOR DavidWeston, 129 Adeliade St., W., Toronto, Ontario, Canada Filed May 31,1963, Ser. No. 284,423 15 Claims. (Cl. 209214) This invention relates toa method and apparatus for the preparation of particles of materialhaving a magnetic susceptibility above a given value from mixtures ofsuch particles with particles having a lower magnetic susceptibility.The invention is particularly directed to the recovery of desiredmaterials from comminuted ores, industrial minerals, industrial gases orthe like.

As is well known in the electromagnetic art, all materials have magneticproperties which are a characteristic of the spin resonance in the outershells of electrons in the atoms of the material. When the atoms arepresent in molecules, this characteristic is retained, and groups ofmolecules associate magnetically into domaines, a domaine being thesmallest magnetic entity that is presently recognized in solidsubstances. When these domaines in a material become oriented thematerial becomes a magnet. In some materials, the domaines cannot beoriented, and such materials are referred to as non-magnetic. Othermaterials exhibit an unusual response to magnetic forces and arereferred to as diamagnetic. By far the largest number of materials, therecovery of which are of interest to man, respond to the application ofmagnetic flux by tending in some degree or other to have their domainesbecome oriented, that is to say, they tend to become magnets. The easewith which a material will become a magnet is a physical constant of thematerial and is called the magnetic susceptibility. Those materials witha high magnetic susceptibility become magnets when subjected to low fluxdensities and vice versa.

When a mixture of particles of materials of different magneticsusceptibility is subjected to a flux density sufficient to cause onlythe particles of a given material in the mixture to become magnets ameans is afforded for separating those particles from the otherparticles in the mixture. This is the fundamental principle of allmagnetic separators.

In my prior application Serial No. 77,895 now abandoned, I disclosed amagnetic separator in which the mixture of particles to be separated issuspended in a vehicle confined in a columnar pathway while beingsubject to the influence of an externally produced magnetic fieldcharacterized by magnetic gradients along the length of the pathway. Byphysically moving the means producing the magnetic field longitudinallywith relation to the columnar pathway 9. separating action wasaccomplished enabling a magnetic concentrate and a magnetic tailing tobe collected at remote ends of the said pathway. The describedarrangement produces particularly good results in the case of materialshaving a magnetic susceptibility which is suflicient to effectivelymagnetize the particles which it is desired to concentrate by subjectingthem to a flux density of up to about 25,000 gauss. When, however, it isnecessary to employ higher flux densities the technology available inthe magnetic art today tends to require a somewhat cumbersome and heavymeans for excitation of the magnetic field and thus the problemsinherent in providing for the physical movement of the magnets andexcitation system make it desirable to provide a system for magneticseparation of such materials wherein provision need not be made for thephysical displacement of the excitation system relative to the pathwaysalong which separation is to be effected.

According to the present invention, I provide such a system whereby themagnetic excitation system is stationary with relation to the pathwaysalong with separation takes place and the design of the equipment isthus free of the mechanical conditions imposed by the increasinglyponderous nature of the excitation system which must be employed toproduce flux densities substantially higher than 25,000 gauss.

According to one embodiment of the invention I provide a solenoid withinthe interior of which are disposed the pathways along which magneticseparation is to take place. Substantially centrally within the solenoidthere is an interior pathway along which a suspension of particles uponwhich separation is to be effected is introduced axially with relationto the solenoid. The said inner pathway extends only part way along theinterior of the solenoid and surrounding it is a generally annularspace. The solenoid has successive windings tapped to the individualphases of a supply of alternating current which is adapted to develop ahelical flow of current around said pathway whereby to produce in theinterior of the solenoid and hence the pathway a magnetic flux densitysufiicient effectively to magnetize those particles of the feed materialwhich it is desired should appear in the concentrate. In operation asuspension of the feed material in a fluid vehicle is introduced to theinner pathway at one end of the solenoid. As the suspension enters theinterior of the solenoid, certain particles thereof become effectivelymagnetized while the vehicle and the remaining particles of feed aresubstantially unaffected by the magnetic field. The magnetic effect ofconnecting successive windings of the solenoid to successive phases of amultiple phase source is that there is created in the space within thesolenoid a successive series of south and north magnetic poles which arediscshaped and substantially at right angles to the axis of thesolenoid. This series of north and south magnetic poles, by virtue ofthe alternation of the current supply, continually advances step-wisealong the space within the solenoid at a linear velocity which is afunction of the frequency of alternation of the current supply. As thesuspension of feed material advances along the interior pathway thoseparticles which become magnetized will move under the influence of themagnetic field rather than under the influence of the movement of thevehicle in which they were introduced while the non-magnetized particlesof feed will continue to move substantially solely under the influenceof the vehicle in which they are suspended. At the end of the innerpathway the vehicle and suspended non-magnetic particles are withdrawnusually in a reverse direction in the annular space between the innerpathway and the solenoid while the magnetized particles continue movingstepwise in their original direction along the solenoid under thecontinuing influence of the magnetic field. Preferably, additionalvehicle is introduced further along the solenoid or from the remote endthereof which serves to clean the magnetic material with which it istheremoving in counter-current and to assist in the transportation ofthe non-magnetic material in the annular space to a point of collection.The magnetic material may be collected at the remote end of thesolenoid.

As will be apparent, the invention as described in general terms may beoperated effectively using gaseous vehicles or liquid vehicles for thematerial which is to undergo separation and the selection of aparticular vehicle will depend in any given case upon the conditions andthe particular materials involved.

In general, and particularly when working with gaseous vehicles, it willbe desirable to have the axis of the sole noid substantially verticaland to introduce the mixture to be separated either upwardly ordownwardly into the interior of the solenoid.

A particular advantage of the foregoing arrangement is that it isfeasible to provide within the one apparatus for not only the basicproduction of a magnetic concentrate and tailing but also for theprovision of a substantial amount of cleaning of the concentrate andtailings during the transport of the centrate to its point of collectionand during transport of the tailing to its point of collection when thelatter takes place in a reverse direction. As will be appreciated, thecross-sectional area of the interior pathway along which the suspensionof particles upon which separation is to be etfected is introduced andthat of the exterior pathway along which the vehicle and suspendednon-magnetic particles are withdrawn can be so selected that thecross-sectional area of the reverse pathway is relatively large incomparison to that of the interior pathway so that the velocity of thefluid vehicle, which in the interior pathway must be sufficient totransport the particulate material, may in the reverse pathway besubstantially below such velocity. Accordingly, magnetized materialwhich has been carried into the reverse pathway by the gaseous vehicleor material which is capable of being efiectively magnetized but which,owing to its reluctance, may require a somewhat longer time period foreffective magnetization than the general run of material which it isdesired to concentrate, may upon becoming magnetized come under theinfluence of the magnetic field and travel with it in a directionopposite to that of the withdrawal of vehicle, eventually to join withthe main concentrate at the point of collection thereof, notwithstandingthe fact that a substantial amount of additional vehicle may -beintroduced along the pathway leading to the point of collection of theconcentrate in countercurrent direction to the transport of themagnetized material under the influence of the magnetic field, whichnewly introduced vehicle augments the volume of vehicle in the reversepathway while carrying non-magnetic particles which have been freed fromthe concentrate into said reverse pathway and ultimately to the point ofcollection of tailing.

The process of the invention, particularly when liquid vehicles areemployed for the transport of the feed material, may be carried out in amanner wherein the separating action is assisted by an increment ofmomentum imparted to the magnetized particles by the movement of themagnetic field. For instance, where the solenoid is horizontal, theinner pathway may extend almost to the end of the solenoid. The vehiclemay be withdrawn from the lower end of the space within the solenoidnear the downstream end thereof along an outer pathway runningconcurrently with the direction of flow in the inner pathway while themagnetic field under the influence of which the magnetized patricles aremoving may be so arranged as to impart to the effectively magnetizedmaterial a velocity higher than that of the liquid vehicle whereby themagnetized particles will be caused to leave the liquid vehicle throughthe surface thereof so that the latter are carried along the innerpathway beyond the point at which the vehicle is withdrawn, to a pointof collection. The entrance to the outer pathway may in this case beprovided with slicer means to enable accurate adjustment for the mosteconomic point of cleanliness of the tailings versus grade of theconcentrate.

The invention and'its operation will be more clearly understood from areading of the following detailed specification taken in conjunctionwith the accompanying drawings wherein FIGURE 1 is a schematicillustration of a portion of a device according to the invention whereinthe separating action takes place and which illustrates the principle onwhich the invention operates;

FIGURE 2 is a schematic illustration of a portion of a device accordingto the invention wherein the material to be separated is introduced in aliquid vehicle and use ismade of an increment of momentum imparted tothe magnetized material to assist the separation thereof from thevehicle and tailings;

FIGURE 2A is a fragmentary longitudinal vertical section illustrating apreferred form of perforation for providing communication between theseparation pathways of FIGURE 2;

FIGURE 2B is a fragmentary longitudinal vertical section through thebottom of casing 17 illustrating a preferred configuration thereof;

FIGURE 3 is an illustration partly in schematic of an electromagneticseparator according to the invention in which the material to beseparated is introduced in a gaseous vehicle;

FIGURE 4 is an illustration partly in schematic of a magnetic separatoraccording to the invention wherein the material to be separated isintroduced in a liquid vehicle;

FIGURE 5 is an illustration partly in schematic of an electromagneticseparator acconding to the invention wherein the material to beseparated is introduced in a liquid vehicle and wherein the separatingaction takes place in a generally horizontal pathway.

Referring now more particularly to the drawings, FIG- URE 1 illustratesgenerally the principle upon which the invention is based. Referring toFIGURE 1, numeral 10 indicates a solenoid successive windings of whichare tapped to successive phases 11, 12 and 13 of a source of alternatingcurrent (not shown by taps 14, 1S and 16 in the manner illustrated: Asillustrated, there are three phases which represents a preferredarrangement particularly because of the readly availability of threephase current supply. However, it is prefectly feasible in place of thethree phase arrangement illustrated to use any multiple phase which itmay be convenient to supply, in which case the taps to the windings ofthe solenoid 10 will be made in a comparable manner in sequence.Additionally, it is to be appreciated that although in the drawing thereis a tap on each and every winding of the solenoid 10 in practice, thetaps may be made at intervals of a number of windings. As will beappreciated by those familar with the electrical art, the solenoid 10)may have a number of layers of windings in which case each tap mayconnect to the windings in each layer at the particular tap intervalwhich has been selected.

Within the solenoid 10 is the cylindrical casing -17 which is suitablycomposed of some non-magnetic material such as fiber-glass, plastic orthe like. The casing 17 need not necessarily be circular in section noris it essential that it entirely fill all of the space within thesolenoid 10 as illustrated. It is preferred, however, to have the casing17 circular and to utilize as much as possible of the space within thesolenoid 10 in order to provide for the maximum economic eificiency.

Within the casing 17 is an inner casing 18 which is made of non-magneticmaterial which suitably may be of the same type as that from which thecasing 17 is made. As will be observed, the casing 18 terminates at 19in an open end within the space within the solenoid 10 and the casing17.

In operation with the current supply turned on, the space within thesolenoid 10 contains a magnetic flux as a result of the current flowingthrough its windings.

The flux density will be substantially uniform on any cross section ofthe solenoid 10 and at any given instant the cross sections of thesolenoid 10 correspond'to the windings connected to the taps 14, 15 and16 will constitute magnetic poles which are in effect planar inconfiguration and disc shaped. These poles Will be arranged alternatelynorth and south as illustrated. Because the current supply isalternating current at each alternation the series of north and southpoles illustrated will move stepwise so that in the interior of thesolenoid 10 there is produced a series of north and south poles movingupwardly in stepwise fashion at a rate of speed determined by thefrequency of the alternating current supply and the distance betweentaps.

In practice, the design of solenoid and the power supply is such as toproduce in the space within the solenoid a flux density which issufficient effectively to magnetize the particular material which it isdesired to separate and to collect. For instance, if the material whichis to be concentrated is hematite, a flux density in the neighbourhoodof twenty to twenty-five thousand gauss might effectively be employed.Other materials of lower magnetic susceptibility than hematite willrequire a higher flux density, and it is within the contemplation of theinvention to produce such higher flux densities up to the region offorty-five thousand gauss and higher depending upon the particularmaterial to be separated.

With the current suuply turned on, a gaseous suspension of a mixture ofsolid particles which is to be separated is introduced through casing18. As a gaseous vehicle, air is in general satisfactory although incertain instances it may be desirable to use other gases such asnitrogen. The velocity of the air will be sufiicient to maintain thesolid material in suspension and may conveniently be of the order of twoto five thousand feet per minute. As the suspended material enters thespace within solenoid 10 while still within casing 18, those particlesof the mixture which have the highest magnetic susceptibility will tendto become magnetized, and when this occurs, they will be attracted tothe poles and their move ment upwardly in casing 18 will tend to becomegoverned by the movement upwardly of the series of north and south poleswhich is produced by the alternating current, so that within casing 18there will be moving along the pathway A defined thereby the gaseousmedium and suspended non-magnetized particles together with themagnetized particles which have come under the influence of the upwardmovement of the north and south poles. As the material and suspendingvehicle issue forth from the end 19 of the casing 18, the gaseousvehicle is made to change its direction of movement and is sentdownwardly through pathway B between the casings 18 and 17 by suitableair motivation means (not shown) carrying with it the bulk of thesuspended non-magnetized particles. Meanwhile, the magnetized particlescontinue to move upwardly in pathway C and are eventually collected insuitable collection means (not shown). Preferably, additional vehicle isintroduced in the upper portion of the solenoid 10 by suitable airsupply means (not shown) whereby the fresh vehicle is in countercurrentwith magnetized particles and tends to entrain and carry away intopathway B the non-magnetized particles which may have been carried alongor entrained with the magnetized particles moving under the influence ofthe magnetic field.

Various refinements of design are necessary in order to achieve fluxdensities of the magnitude contemplated within the solenoid 10 and todissipate the heat produced. Such refinements of design are well knownin the electromagnetic art and include conventional means fordissipating the heat produced in the solenoid. For achieving fluxdensities of up to the neighbourhood of 10,000 gauss using conventionalwindings, use may be made of disc shaped sections of solenoid havinginterspaced discs of high heat conducting material such as copper oraluminum which extend outwardly from the solenoid and may be air cooled.For flux densities in the to 20,000 gauss range, use may be made ofcooling coils or discs imbedded in the windings of the solenoid throughwhich a conventional coolant may be circulated. For achieving fluxdensities of between twenty and thirty thousand gauss, the windingsthemselves of the solenoid may be formed from copper or the like tubingthrough which there may be circulated a refrigerated brine solution.However, as one approaches the upper end of this range of fluxdensities, increased electrical efficiency may be achieved through theuse of special alloys whose coeflicient of electrical resistance exhibita pronounced drop within ranges of temperatures which may be achievedwith refrigerated brine. Such materials are well known in the art andinclude, for instance, high purity copper containing less than one tenthousandth of 1% impurity. The achievement of flux densities higher thanabout thirty thousand gauss renders desirable the employment oftemperatures for the excitation system of down to about Kelvin. Suchtemperatures may readily be achieved through the use of tubularconductors through which a coolant such as liquid nitrogen or helium ispassed. As the flux density is increased, special alloys havingparticularly low electrical resistance at low temperatures such ascertain niobium tin alloys become desirable in order to make morereasonable the demands upon the cooling system which vary as is wellknown with the power requirements of the system. At these highintensities of field, the electrical resistance of the excitation systembecomes a governing factor because as will be appreciated, the heatproduced in overcoming electrical resistance is produced within theconductors of the system and works against the refrigeration systemwhich cannot produce a temperature materially lower than that of theliquefaction temperature of the coolant medium. It therefore becomesincreasingly important to utilize a design for the excitation systemwhich involves as little electrical resistance as possible as the fluxdensity of the magnetic field increases. For very high flux densities upto about 75,000 gauss, it may be found desirable to operate attemperatures as low as about 10 Kelvin, utilizing liquid helium as thecoolant and employing alloys for the coils of the solenoid which arecomposed of material whose resistance approaches zero at suchtemperatures. In such cases, techniques common in the cryogenic art willbe necessary to maintain an efficient operating temperature for theexcitation system.

It will be obvious to those skilled in the art that Where the fluxdensities to be employed according to the invention are such as torequire the maintenance of temperatures substantially below roomtemperature, provision must be made for adequate insulation of thesolenoid. Where'the vehicle used for transport of the feed material isliquid (e.g. brine), insulation of the separation pathways within thespace inside the solenoid is not needed down to temperatures of about 21below zero centigrade if the vehicle itself is refrigerated to atemperature comparable, with that of the excitation system. Similarly,where a gaseous vehicle isemployed, insulation of the separationpathways from the solenoid may not be necessary where the excitationsystem is not maintained below about 21 below zero centigrade exceptingunder operating conditions Where high temperature and humidity of theambient air introduce condensation problems and problems of heatremoval. However, when operating the excitation system below about 21below zero centigrade, it will be most important to provide for adequatethermal insuation of the separation pathways within the solenoid fromthe excitation system.

FIGURE 2 is a schematic illustration which illustrates the separatingaction of the embodiments of the invention wherein the solenoid ishorizontal and the material to be separated is introduced in a liquidvehicle. Referring to FIGURE 2, the solenoid 10 having taps 14, 15 and16 connected to the three phases 11, 12 and 13 of a threephasealternating current supply (not shown) in the same fashion as hasalready been explained in connection With FIGURE 1 has its coilsimmersed in a sub-zero cooling system 20 through which there may becirculated a liquid coolant such as helium or hydrogen in order tomaintain a coil temperature of between about 20 F. and about 10 K.depending upon the particular flux density which the apparatus has beendesigned to produce. The coils themselves may be of pure copper or ofspecial alloys such as niobium tin, again depending upon the fluxdensity which is to be achieved. Within the solenoid 10 is a layer ofthermal insulation 21. Inside the layer of thermal insulation 21 is thecasing 17 which defines the pathway along which material to be separatedis to be passed. At the lower side of the casing 17 and radially outwardthereof is a second casing 18a which communicates with the interior ofthe casing 17 and defines a pathway for the removal of tailing.Preferably, the position of the opening, which provides communicationbetween the interior of the casing 17 and the interior of the casing18a, is adjustable as will be hereinafter explained.

In operation, the material to be treated is introduced into the casing17 as a slurry in a liquid vehicle which may be water or brine at a ratewhich is such that at the inlet (left hand) end of the solenoid 10, thecasing 17 is completely filled with slurry. Liquid is continually beingwithdrawn through the casing 18a by a pumping means (not shown) atsubstantially the same rate as the slurry is being introduced to thecasing 17. This results in the formation of a liquid surface 24 ofgenerally parabolic shape extending from the upper side of the casing 17to the end 22 of the entrance to casing 18a.

The excitation of the solenoid is such as to produce a flux densitysufiicient effectively to magnetize the particles which it is desired inthe concentrate and tap interval and frequency of alternation of thecurrent supply is such as to produce a rate of progression of magneticwaves along the solenoid which is substantially higher than the velocityof flow of the slurry. The effectively magnetized particles come underthe influence of the magnetic field and are attracted to the planes ofthe poles produced thereby in the same manner as has been explained inconnection with FIGURE 1. This material begins to move at a highervelocity than that of the liquid vehicle, and as the slurry moves alongpathway A, the increase in velocity will cause the material to leave thesurface 24 and be carried under the influence of the magnetic field intopathway C. The additional velocity imparted to the magnetized materialtends to carry it in a generally parabolic path beyond the point 22 andto a point of collection (not shown) at the end of pathway C. Thevehicle and particles of slurry which have not become magnetized areuninfluenced by the magnetic field and continue to move in the vehicleinto pathway B within casing 18A to a point of tailings collection (notshown).

Since the magnetized particles are not supported by the magnetic fieldagainst the pull of gravity, the parabolas along which some of theseparticles are moving will tend to carry them into pathway B. In order toobtain the optimum cut-off point as between concentrate and tailing, theposition of the end 22 of the opening is adjustable to permit adjustmentof the cut; preferably the opening may be covered by a punched platewhich is provided with perforations over an area 25. A preferred designof perforation is shown in section in FIGURE 2A. As will be observed,the perforations are each provided with a ramp 26 and a drainage lip 27which underlies the ramp 26. Slurry landing on the portion 25 willimpinge almost directly on the ramps 26 losing most of its forwardvelocity. Magnetic particles contained in such slurry Will be picked upand carried along by the magnetic field while liquid vehicle andnon-magnetic particles will tend to be drawn out along drainage lip 27owing to the reduced pressure created at point 28 by the flow of slurryin pathway B. In order to take full advantage of the velocity impartedto the magnetized particles by the magnetic field, the lower side ofcasing 17 may be modified as illustrated in section in FIGURE 2B, so asto impart a hydrofoil profile thereto which over the portion 29 willimpart a substantial upward increment of velocity to the vehicle and theparticles therein. This component of upward velocity will be impartedboth to the magnetic and non-magnetic particles contained in the vehicleadjacent the portion 29 of the hydrofoil but owing to the highervelocity of the magnetic particles will impart to the latter a flattertrajectory and tend to permit fewer of the magnetic particles to enterthe pathway B. If desired,

the communication between pathway B and pathway A i employed for theintroduction of the material to be sep arated is gaseous, the mostcommonly employed vehicle being air. As will be observed, the solenoid10 is here formed in the shape of an inverted U as is the casing 17which is surrounded by it. The material to be separated entersyertically upwardly through casing 18 suspended in an airstream. Asuitable feed may, for instance, be the discharge from an airswept drycomminution mill. The velocity of the airstream may be of the order offrom about two thousand to four thousand feet per minute. The solenoid10 is connected to the three phases 11, 12 and 13 by taps 14, 15 and 16in the same manner as has already been explained in connection with FIGURE 1. The flux density of the field is such as to be calculated toeffectively magnetize the particles of material which it is desired tohave in the concentrate and the tap interval and the frequency is suchas to be calculated to produce a linear velocity for the magnetic waveproduced within the solenoid 10 which is substantially the same as thevelocity of the air in which the material to be separated is introducedwithin casing 18, i.e. a velocity of the order of two thousand to fourthousand feet per minute. As the material carried by the air in casing18 comes under the influence of the solenoid It the particlessusceptible to magnetization at the flux density produced withinsolenoid 10 commence to become magnetized and move under the influenceof the magnetic field. Preferably, baflies 30 are placed within casing18 in order to minimize occlusion of non-magnetic materials in theconcentrations of magnetized material which form along the planes of thepoles of the magnetic field. As the material and vehicle come to the endof pathway A, most of the magnetic susceptible material will have becomemagnetized and will be moving substantially solely under the influenceof the travelling magnetic field, and will, therefore, continue to becarried along pathway C over the top of the inverted U. The vehicle andnon-magnetic particles is withdrawn downwardly along pathway B by fan31, the non-magnetic solids being collected in cyclone 32, and thegaseous vehicle departing through conduit 33 from which it may berecirculated for purposes of resuspending more material tobe separatedfor introduction into casing 18 or, if the source of material to beseparated is an airswept mill to the inlet side of such mill. As thevehicle and non-magnetic material is being withdrawn through pathway B,it may still contain the most difiicult to magnetize particles of thematerial that it is desired to concentrate. Where such particles becomemagnetized during passage downwardly in pathway B, they will tend to bedrawn upwardly under the influence of the magnetic field concurrent tothe vehicle. As will be appreciated, the cross-sectional area of pathwayB is substantially greater than that of pathway A, and accordingly thevelocity of the gas flow therein will be substantially lower than thatin pathway A, thus making it feasible to withdraw magnetized particlesupward in a direction countercurrent to the flow of gas. As will beobserved, pathway C extends over the crest of the inverted U anddownwardly intothe other leg of the inverted U. During its downwardpassage, the magnetized material is subjected to a cleaning action bymeans of a plurality of jets of air produced by nozzles 31 which aresupplied by the fan 32. Nonmagnetic cleanings are carried back over thecrest of the U and joined the original vehicle and tailings descendingin pathway B. The concentrate drops into the hopper 34 and is extractedthrough air lock 35 from whence it may pass to a subsequent treatmentstage.

In the apparatus illustrated in FIGURE 4, the material to be treated isintroduced in a liquid vehicle which may be water or brine. The slurrytank 40 equipped with float valve 41 for maintaining a constant level ofslurry therein is supplied with liquid and solid feed in anyconventional manner under control of the said float valve 41 whichcontrols valve 41a in feedline 41b. The slurry is kept suspended byagitator 43 which is preferably associated with shroud 43a. Pump 44pumps the slurry from slurry tank 40 into conduit 45 which is made ofnonmagnetic material and extends upwardly within the nonmagnetic casing17 which is surrounded by a solenoid which is connected by taps 14, and16 to the phases 11, 12 and 13 of a three phase current supply in thesame manner as illustrated in FIGURE 1. The lower end of the casing 17communicates with conduit 46 through which slurry pump 47 controllablywithdraws the vehicle and suspended tailings. The pumping rate of pumps45 and 47 is controlled in conventional manner to maintain a constantlevel of slurry within casing 17. The top of casing 17 is elbowed sothat the open end 48 thereof faces in a generally downward directiontowards concentrate collecting pan 49. The coils of solenoid 10 areenclosed within an insulated cooling system 50 through which arefrigerated liquid is circulated to maintain the coils solenoid at adesired low temperature. The type of refrigerating system will dependupon the flux density at which the apparatus is designed to operate andmay be for instance brine at temperatures of down to about 21 below zeroC. or liquid helium or nitrogen where the operating temperature is to bebelow about 21 C. Details of the refrigeration system are not shown assuch systems are conventional. Between the coils of solenoid 10 and thecasing 17, there is a layer of insulation 51 which is adapted to protectthe liquid vehicle from temperatures which would cause freezing withinpathways A and B. In operation, the slurry is fed into conduit 45 whichleads it upwardly within the space of solenoid 10 along pathway A. Asthe slurry rises along pathway A, the particles of solids which becomeeffectively magnetized at the flux density employed will becomemagnetized and will tend to move under the influence of the magneticfield in the manner which has already been explained. These particleswill on leaving pathway A continue to move under the influence of themagnetic field through the surface 52 of the slurry and into pathway Cwhere they are discharged through the end 48 of casing 17 and collectedin the concentrate collection pan 49. The liquid vehicle and magnetizedmaterial moves radially outward into pathway B on leaving the upper endof the conduit 45 and flows downwardly under the influence of pump 47.On passing downwardly through pathway B, any particles of magneticmaterial which may have been carried over in a vehicle either because offailure to become elfectively magnetized through pathway A or byocclusion will tend -.to be picked up by the magnetic field and movedcountercurrently upwardly in pathway B to join the concentrate inpathway C.

In operation, the flow rate of the slurry up pathway A will be adjustedto correspond with the rate of progression of the series of north andsouth poles along pathway A produced by the alternating current supply,the actual rates depending upon the material undergoing treatment.Generally speaking, the speeds involved will be sufficiently low thatthe vehicle and non-magnetic material will not tend by virtue of theirmomentum to rise higher than the surface 52 of the slurry so that therewill be no tendency for vehicle and non-magnetic material to be carried'over the lip 53 at the bottom of the elbow at the end of casing 17.

. In the embodiment illustrated in FIGURE 5, in which the feed materialis again introduced in a liquid vehicle,

the supply means for feed material is the same as that employed inconnection with FIGURE 4. However, in this case supply of feed throughconduit 60* is controlled by the valve 61 as the slurry is feddownwardly by gravity. The rate of speed of feed of the slurry is suchthat the conduit 60 is full at the point at which it enters the pathwayA in the space within the solenoid 10, but soon after entering pathway Athe surface of the slurry will break away from the upper surface of theconduit 60 in a generally sloping surface 62. In the bottom of theconduit 60 in advance of the perforated plate 63 which affordscommunication between pathways A and B there is a hydrofoil section 64-which acts as a sort of weir over which the slurry must pass on its wayto the section of perforated plate 63. In operation, the hydrofoil 64serves to give an upward increment of momentum to the magnetizedmaterial in the slurry giving such material a trajectory which will tendto carry it beyond the perforated section 63 and into pathway C andthence into the concentrate collector pan 65. The vehicle andnon-magnetic tail-ings flow outwardly by gravity through conduit 66. Theperforated section 63 is preferably constructed in the mannerillustrated in FIGURE 2A to minimize the amount of magnetic concentratewhich will pass downwardly into pathway B. The position of theperforated section, and the end of the opening 22 may be adjusted bylever 67.

The frequency of the alternating current and the spacing of the taps inthe embodiment illustrated in FIGURE 5 will be such as to produce aprogression of north and south poles along pathways A and C which issubstantially greater than the linear velocity of the pulp which isbeing introduced so that the magnetized material will acquire anincrement of momentum which will tend to shoot it through pathway C witha considerable velocity. This effect may be increased by progressivelyincreasing the tap interval along the length of the solenoid 10 wherebythe rate of travel of the progression of north and south poles willprogressively increase along the length of the solenoid 10.

It will be appreciated that in connection with the embodimentillustrated in FIGURE 5, it is not necessary that the solenoid 10 behorizontal as illustrated. The solenoid and the pathways thereincontained may tilt upwardly or downwardly at a substantial angle fromthe horizontal. Where the solenoid tilts upwardly, it will beappreciated that it will be necessary to have the communication betweenconduit 66 and pathway A below the level of the liquid surface 62 and toinclude pumping means within pathway B.

What I claim as my invention is:

1. A process for separating particles of a solid material having atleast a predetermined magnetic susceptibility from a mixture of saidparticles with other solid particles having a lower magneticsusceptibility, said process comprising: helically developing a flow ofmulti-phase alternating current around a tubular space whereby to formand maintain within said tubular space a mag-netic field characterizedby a plurality of planar north and south poles alternately disposedtransversely to the longitudinal axis and substantially across the wholecross section of said tubular space, said magnetic field having aSllfl'lCiCIlt flux density effectively to ma gnetize said particles ofsolid material having at least said predetermined magneticsusceptibility: forming a suspension of said mixture in a fluid vehicle:introducing said suspension and advancing the same along a first pathwaywithin said tubular space and extending lengthwise thereof, advancingsaid poles stepwise along said tubular space whereby the particles ofmaterial within said suspension which are effectively magnetized areadvanced along said first pathway under the influence of the stepwiseadvancement of said poles: discharging said suspension from said firstpathway into said tubular space: withdrawing along a second pathwaywithin said tubular space said fluid vehicle and suspended solidmaterial which is not eflectively magnetized and subsequently collectingsuch material: and continuing to advance said effectively magnetizedparticles within .said tubular space under the influence of the stepwisemovement of said poles to a point of collection and collecting the same.

a 2. A process for separating particles of a solid material having atleast a predetermined magnetic susceptibility from a mixture of saidparticles with other solid particles having a lower magneticsusceptibility, said process comprising: helically developing a flow ofmulti-phase alternating current around a tubular space whereby to formand maintian within said tubular space a magnetic field characterized bya plurality of planar north and south poles alternately disposedtransversely to the longitudinal axis and substantially across the wholecross section of said tubular space, said magnetic field having asufficient fl'ux density effectively to magnetize said particles ofsolid material having at least said predetermined magneticsusceptibility: forming a suspension of said mixture in a fluid vehicle:introducing said suspension and advancing the same along a first pathwaywithin said tubular space and extending lengthwise thereof, advancingsaid poles stepwise along said tubular space whereby the particles ofmaterial within said suspension which are effectively magnetized areadvanced along said first pathway under -the influence of the stepwiseadvancement of said poles:

discharging said suspension vfrom said first pathway into said tubularspace: withdrawing in a reverse direction along a sec-nd pathway withinsaid tubular space said fluid vehicle and suspended solid material whichis not effectively magnetized and subsequently collecting such material:and continuing to advance said effectively magnetized particles withinsaid tubular space under the influence of the stepwise movement of saidpoles to a point of collection and collecting the same.

3. A method of separating particles consisting essentially of materialhaving a magnetic susceptibility above a given value from a mixture ofparticles of said material with particles of material having a lowermagnetic susceptibility, said method comprising: suspending said mixturein a stream of gaseous vehicle which is moving at suflicient velocity totransport said mixture; directing said stream and suspended mixture in asubstantially vertical direction while confining said stream within aninner pathway; helically developing a flow of multi-phase alternatingcurrent around said pathway whereby to form and maintain within saidpathway a magnetic field characterized by a plurality of planar northand south poles alternately disposed transversely to the longitudinalaxis and substantially across the whole cross section of said pathway,said magnetic field having a sufficient flux density effectively tomagnetize said particles of solid material having at least saidpredetermined magnetic susceptibility; synchronously moving all of saidpoles stepwise along said |pathway concurrently with said stream wherebythe effectively magnetized particles move under the influence of thestepwise movement of said poles, but the particles of lower magneticsusceptibility are substantially uninfluenced by said magnetic flux;providing an outer pathway substantially coaxial with and surroundingsaid inner pathway and continuing beyond the same, said outer pathwaybeing subject to the said magnetic flux across substantially its wholecross section; directing said gaseous vehicle into said outer pathway ina reverse direction, whereby the particles of lower magneticsusceptibility are carried thereby in said reverse direction in saidouter pathway, while the effectively magnetic particles continue to movein the original direction under the influence of the stepwise movementof said poles; and collecting separately the particles carried by saidgaseous vehicle and the particles moving under the influence of saidmagnetic fiux.

4. A method of separating particles consisting essentially of materialhaving a magnetic susceptibility above a given value from a mixture ofparticles of said mate rial with particles of material having a lowermagnetic susceptibility, said method comprising: suspending said mixturein a stream of liquid vehicle; directing said stream and suspendedmixture in a substantially vertical direction while confining saidstream within an inner pathway; helically developing a flow ofmulti-phase alternating current around said pathway whereby to vform andmaintain within said pathway a magnetic field characterized by aplurality of planar north and south poles alternating disposedtransversely to the longitudinal axis and substantially across the wholecross section of said pathway, said magnetic field having a sufficientflux density eflectively to magnetize said particles of solid materialhaving at least said predetermined magnetic susceptibility;synchronously moving all of said poles stepwise along said pathwayconcurrently with said stream whereby the effectively magnetizedparticles move under influence of the stepwise movement of said poles,but particles of lower magnetic susceptibility are substantiallyuninfluenced by said magnetic flux; providing an outer pathwaysubstantially coaxial with and surrounding said inner pathway andcontinuing beyond the same, said outer path way being subject to thesaid magnetic flux across sub stantially its whole cross section;directing said liquid vehicle into said outer pathway in a reversedirection, whereby the particles of lower magnetic susceptibility arecarried thereby in said reverse direction in said outer pathway, whilethe effectively magnetic particles continue to move in the originaldirection under the influence of the stepwise movement of said poles;and collecting sep arately the particles carried by said liquid vehicleand the particles moving under the influence of said magnetic flux 5. Aprocess for separating particles of solids material having at least apredetermined magnetic susceptibility from a mixture oi said particleswith other solid particles having a lower magnetic susceptibility, saidprocess comprising; helically developing a flow of multi-phasealternating current around a tubular space whereby to form and maintainwithin said tubular space a magnetic field characterized by a pluralityof planar north and south poles alternately disposed transversely to thelongitudinal axis and substantially across the whole cross section ofsaid tubular space, said magnetic field having a s-uflicient fluxdensity effectively to magnetize said particles of solid material havingat least said predetermined magnetic susceptibility: forming asuspension of said mixture in a fluid vehicle: introducing saidsuspension and advancing the same along a first pathway within saidtubular space and extending lengthwise thereof, advancing said polesstepwise along said tubular space whereby the particles of materialwithin said suspension which are effectively magnetized are advancedalong said first pathway under the influence of the stepwise advancementof said poles: discharging said suspension from said first pathway intosaid tubular space: withdrawing along a second pathway in the lower sideof and within said tubular space said fluid vehicle and suspended solidmaterial which is not effectively magnetized and subsequently collectingsuch material: and continuing to advance said effectively magnetizedparticles within said tubular space under the influence of the stepwisemovement of said poles across substantially the whole cross section ofsaid tubular space to a point of collection and collecting the same.

6. The process defined in claim 5 wherein said tubular space issubstantially horizontal.

7. A process for separating particles of a solid material having atleast a predetermined magnetic susceptibility from a mixture of saidparticles with other solid particles having a lower magneticsusceptibility, said process comprising: helically developing a flow ofmultiphase alternating current around a tubular space whereby to formand maintain within said tubular space a magnetic field characterized bya plurality of planar north and south poles alternately disposedtransversely to the longtiudinal axis and substantially across the wholecross section of said tubular space, said magnetic field having asufficient flux of density effectively to magnetize said particles ofsolid material having at least said predetermined magneticsusceptibility: forming a suspension of said mixture in a fluid vehicle:introducing said suspension and advancing the same along a first pathwaywithin said tubular space and extending lengthwise thereof, advancingsaid poles stepwise along said tubular space whereby the particles ofmaterial within said suspension which are effectively magnetized areadvanced along said first pathway under the influence of the step wiseadvancernent of said poles: discharging said suspension from said firstpathway into said tubular space: withdrawing in a reverse directionalong a second pathway within said tubular space said fluid vehicle andsuspended solid material which is not eflectively magnetized andsubsequently collecting such material: and continuing to advance saideffectively magnetized particles within said tubular space under theinfluence of the stepwise movement of said poles through a cleaningzone, introducing additional vehicle within said cleaning zone in adirection countercurrent to the movement of said effectively magnetizedparticles and advancing said effectively magnetized particles to a pointof collection and collecting the same.

8. Apparatus for the production of concentrates from particulatemixtures of materials having different magnetic susceptibilities, saidapparatus comprising: a tubular space having a conductor wound helicallyaround and adjacent the surface thereof in the form of a solenoid, saidtubularspace defining a confined pathway through which material to beseparated is passed, said confined pathway being composed ofnon-magnetic material, said solenoid being adapted, when appropriatelyenergized to produce flux densities in the space within its coils of amagnitude sufficient effectively to magnetize the material in saidparticulate mixtures which it is desired to concentrate; excitationmeans for said solenoid adapted to energize the latter to produce saidsuflicient flux densites, said excitation means comprising a multiphasealternating current power supply, a series of taps connecting coils ofsaid, solenoid to each, of the phases of said power supply, said tapsbeing arranged in regular sequence along the length of the solenoid, thetaps of a series connected to one phase being followed by the tap of aseries connected to a later phase, and the taps of the series connectedto the latest of said phases being followed by the taps of the seriesconnected to the earliest of phases, where-by on supply of power to saidsolenoid a series of planar north and south poles are formed acrosssections of said solenoid corresponding to the positions of said taps,said series of north and south poles advancing along said solenoid fromtap to tap at a rate determined by the frequency of the power supply;said tubular space extending axially into the space with in the coils ofsaid solenoid, and defining within said space a separation pathway formaterial; means for supplying and advancing along said separationpathway, a particulate material upon which separation is to be effectedsuspended in a fluid vehicle; a second tubular casing means composed ofnon-magnetic material within the coils of said solenoid separate frombut communicating with the end of said separation pathway and defining asecond pathway; means associated with said second pathway forwithdrawing tailing and vehicle therealong; and means for collectingconcentrate from the end of the space within the coils of said solenoid.

9. Apparatus for the production of concentrates from particulatemixtures of materials having different magnetic susceptibilities, saidapparatus comprising: a tubular space having a conductor wound helicallyaround and adjacent the surface thereof in the form of a solenoid,

said tubular space defining a confined pathway through which material tobe separated is passed, said confined pathway being composed ofnon-magnetic material, said solenoid being adapted, when appropriatelyenergized to produce flux densities in the space within its coils of amagnitude sufficient effectively to magnetize the material in saidparticulate mixtures which it is desired to concentrate; excitationmeans for said solenoid adapted to enegize the latter to produce saidsufficient flux densities, said excitation means comprising a multiphasealternating current power supply, a series of taps connecting coils ofsaid solenoid to each of the phases of said power supply, said tapsbeing arranged in regular sequence along the length of the solenoid, thetaps of a series connected to one phase being followed by the tap of aseries connected to a later phase, and the taps of the series connectedto the latest of said phases being followed by the taps of the seriesconnected to the earliest of phases, whereby on supply of power to saidsolenoid a series of planar north and south poles are formed acrosssections of said solenoid corresponding to the positions of said taps,said series of north and south poles advancing along said solenoid fromtap to tap at a rate determined by the frequency of the power supply;said tubular space extending axially into the space within the coils ofsaid solenoid, and defining within said space a separation pathway formaterial; means for supplying and advancing along said separationpathway, a particulate material upon which separation is to be effectedsuspended in a fiuid vehicle; a second tubular casing means composed ofnon-magnetic material within the coils of said solenoid separate frombut communicating with the end of said separation pathway and defining asecond pathway; means associated with said second pathway forwithdrawing tailing and vehicle therealong in a reverse direction; andmeans for collecting concentrate from the end of the space within thecoils of said solenoid.

10. Apparatus as defined in claim 9 wherein said second tubular casingis of larger diameter than and concentric with said first tubular casingwhereby to form between the walls of said first and second tubularcasings a pathway within said solenoid for the withdrawal of vehicle andtailings in a reverse direction.

11. Apparatus as defined in claim 10 comprising means for theintroduction of fresh vehicle within said second tubular casing beyondthe end of said first tubular casing for countercurrent cleaning ofconcentrate.

12. Apparatus as defined in claim 10 wherein the windings of saidsolenoid are formed from tubes of a metallic substance selected from thegroup consisting of pure copper and niobium-tin alloys of low electricalresistance at low temperatures and in which means are provided forcirculating a low temperature refrigerant through the tubes forming saidcoils.

13. Apparatus for the production of concentrates from particulatemixtures of materials having different magnetic susceptibilities, saidapparatus comprising: a tubular space having a conductor wound helicallyaround and adjacent the surface thereof in the form of a solenoid, saidtubular space defining a confined pathway through which material to beseparated is passed, said confined pathway being composed ofnon-magnetic material, said solenoid being adapted, when appropriatelyenergized to produce flux densities in the space within its coils of amagnitude suflicient effectively to magnetize the material in saidparticulate mixtures which it is desired to concentrate; excitationmeans for said solenoid adapted to energize the latter to produce saidsufficient flux densities, said excitation means comprising a multiphasealternating current power supply, a series of taps connecting coils ofsaid solenoid to each of the phases of said power supply, said tapsbeing arranged in regular sequence along the length of the solenoid, thetaps of a series connected to one phase being followed by the tap of aseries connected to a later phase, and the taps of the series connectedto the latest of said phases being followed by the taps of the seriesconnected to the earliest of phases, whereby on supply of power to saidsolenoid a series of planar north and south poles are formed acrosssections of said solenoid corresponding to the positions of said taps,said series of north and south poles advancing along said solenoid fromtap to tap at a rate determined by the frequency of the power supply;said tubular space extending axially into the space within the coils ofsaid solenoid, and defining within said space a separation pathway formaterial; means for supplying and advancing along said separationpathway, a particulate material upon which separation is to be eflectedsuspended in a liquid vehicle; a second tubular casing means composed ofnon-magnetic material Within the coils of said solenoid separate frombut communicating with said separation pathway and defining a secondpathway; means associated with said second pathway for withdrawingtailing and vehicle therealong concurrently with the material in saidfirst pathway; means for collecting concentrate from the end of thefirst pathway; and means for collecting tailings from the end of saidsecond pathway.

14. Apparatus as defined in claim 13 wherein said solenoid is disposedsubstantially horizontally and said second pathway is disposed at thelower side of said first pathway.

15. Apparatus for the production of concentrates from particulatemixtures of materials having different magnetic susceptibilities, saidapparatus comprising: a tubular space having a conductor wound helicallyaround and adjacent the surface thereof in the form of a solenoid, saidtubular space defining a confined pathway through which material to beseparated is passed, said confined pathway being composed of nonmagneticmaterial, said solenoid being adapted, when appropriately energized toproduce flux densities in the space within its coils of a magnitude ofat least 20,000 gauss that will efiectively magnetize the material insaid particulate mixtures which it is desired to concentrate; excitationmeans for said solenoid adapted to energize the latter to produce saidsufficient flux densities, said excitation means comprising a multiphasealternating current power supply, a series of taps connecting coils ofsaid solenoid to each of the phases of said power supply, said tapsbeing arranged in regular sequence along the length of the solenoid, thetaps of a series connected to one phase being followed by the tap of aseries connected to a later phase, and the and the taps of the seriesconnected to the latest of said phases being followed by the taps of theseries connected to the earliest of phases, whereby on supply of powerto said solenoid a series of planar north and south poles are formedacross sections of said solenoid corresponding to the positions of saidtaps, said series of north and south poles advancing along said solenoidfrom tap to tap at a rate determined by the frequency of the powersupply, the spacing between said taps being greater at the downstreamend of said solenoid than at the upstream end thereof; said tubularspace extending axially into the space Within the coils of saidsolenoid, and defining within said space a separation pathway formaterial; means for supplying and advancing along said separationpathway, a particulate material upon which separation is to be effectedsuspended in a liquid vehicle; a second tubular casing means composed ofnon-magnetic material within the coils of said solenoid separate frombut communicating with said separation pathway and defining a secondpathway; means associated with said second pathway for withdrawingtailing and vehicle therealong concurrently with the material in saidfirst pathway; means for collecting concentrate from the end of thefirst pathway; and means for collecting tailings from the end of saidsecond pathway.

References Cited by the Examiner UNITED STATES PATENTS 619,636 2/ 1889Trustedt 209227 2,056,426 10/ 1936 Frantz 209-232 2,596,743 5/1952Vermieren 210222 2,973,096 2/1961 Greaves 210222 X 3,045,821 7/1962Cavanagh 209-214 FOREIGN PATENTS 215,362 6/ 1958 Australia.v

160,503 6/ 1941 Austria.

646,482 8/1962 Canada.

HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner.

1. A PROCESS FOR SEPARATING PARTICLES OF A SOLID MATERIAL HAVING ATLEAST A PREDETERMINED MAGNETIC SUSCEPTIBILITY FROM A MIXTURE OF SAIDPARTICLES WITH OTHER SOLID PARTICLES HAVING A LOWER MAGNETICSUSCEPTIBILITY, SAID PROCESS COMPRISING: HELICALLY DEVELOPING A FLOW OFMULTI-PHASE ALTERNATING CURRENT AROUND A TUBULAR SPACE WHEREBY TO FORMAND MAINTAIN WITHIN SAID TUBULAR SPACE A MAGNETIC FIELD CHARACTERIZED BYA PLURALITY OF PLANAR NORTH AND SOUTH POLES ALTERNATELY DISPOSEDTRANSVERSELY TO THE LONGITUDINAL AXIS AND SUBSTANTIALLY ACROSS THE WHOLECROSS SECTION OF SAID TUBULAR SPACE, SAID MAGNETIC FIELD HAVING ASUFFICIENT FLUX DENSITY EFFECTIVELY TO MAGNETIZE SAID PARTICLES OF SOLIDMATERIAL HAVING AT LEAST SAID PREDETERMINED MAGNETIC SUSCEPTIBILITY:FORMING A SUSPENSION OF SAID MIXTURE IN FLUID VEHICLE: INTRODUCING SAIDSUSPENSION AND ADVANCING THE SAME ALONG A FIRST PATHWAY WITHIN SAIDTUBULAR SPACE AND EXTENDING LENGTHWISE THEREOF, ADVANCING SAID POLESSTEPWISE ALONG SAID TUBULAR SPACE WHEREBY THE PARTICLES OF MATERIALWITHIN SAID SUSPENSION WHICH ARE EFFECTIVELY MAGNETIZED ARE ADVANCEDALONG SAID FIRST PATHWAY UNDER THE INFLUENCE OF THE STEPWISE ADVANCEMENTOF SAID POLES: DISCHARGING SAID SUSPENSION FROM SAID FIRST PATHWAY INTOSAID TUBULAR SPACE: WITHDRAWING ALONG A SECOND PATHWAY WITHIN SAIDTUBULAR SPACE SAID FLUID VEHICLE AND SUSPENDED SOLID MATERIAL WHICH ISNOT EFFECTIVELY MAGNETIZED AND SUBSEQUENTLY COLLECTING SUCH MATERIAL:AND CONTINUING TO ADVANCE SAID EFFECTIVELY MAGNETIZED PARTICLES WITHINSAID TUBULAR SPACE UNDER THE INFLUENCE OF THE STEPWISE MOVEMENT OF SAIDPOLES TO A POINT OF COLLECTION AND COLLECTING THE SAME.